std::codecvt_utf8_utf16 is a std::codecvt facet which encapsulates conversion between a UTF-8 encoded byte string and UTF-16 encoded character string. If Elem is a 32-bit type, one UTF-16 codepoint will be stored in each 32-bit character of the output sequence. This codecvt facet can be used to read and write UTF-8 files, both text and binary.